I used photoshop and a screenshot of one of my favorite scenes..
I hand traced most of it or used contrasting tools.. anyways you can trace your own scene or you can use this Free Batman Joker pumpkin stencil based on a scene from the movie the Dark Knight.. Provided by your's truly (<--yes i'm trying to improve SEO lol)
Step 1: Print out your design and tape it your pumpkin
Print out your design and tape it your pumpkin and use a needle or something pointy to trace your design into the pumpkin